Signal Craft
Generators, waveforms, harmonics, and safe practice: from sine purity to paradox mixing experiments.
What is Signal Craft?
FoundationsSignal craft is the art of shaping waves with intention — selecting sources, waveforms, amplitudes, and routings to create clean, controllable energy for experiments, sound art, and resonance builds. Start simple (single sine, moderate voltage), measure faithfully, and iterate.
Generators & Sources
ToolsCommon Sources
- Function/AWG (e.g., Siglent, Rigol): sines, sweeps, duty, bursts.
- RF gens: stable HF; couple via matching/attenuators.
- Audio interface + DAW: complex stacks; export sessions.
- DDS microcontrollers: portable, programmatic patterns.
Which to pick?
- Audio experiments: AWG or DAW → audio amp.
- Coil tests: AWG → amp → coil; monitor Vpp & temperature.
- RF cavities: RF gen + probes; always attenuate appropriately.
| Source | Pros | Considerations |
|---|---|---|
| Function / AWG | Flexible waveforms, sweeps, duty, AM/FM | Audio-range amps often needed for power |
| RF Signal Gen | Stable HF signals, fine freq control | Low output power; impedance/attenuators needed |
| Audio Interface + DAW | Complex layers, envelopes, export | Limited to ~20 kHz; needs calibration |
| Microcontroller DDS | Cheap, programmable, compact | Jitter/aliasing if poorly filtered |
Waveforms & Harmonics
SpectraDifferent waveforms carry different harmonic content. Sine is pure (single frequency). Square, triangle, and sawtooth contain overtone series that excite many modes at once.
Common Waveforms
Square: odd harmonics 1/n; Triangle: odd harmonics 1/n²; Saw: all harmonics 1/n.
Duty Cycle (Pulse / PWM)
Duty changes spectral energy. Narrow pulses spread energy; 50% duty maximizes odd harmonics (square).
Safe Practice & Levels
EssentialsGuardrails
- Start low: amplitude, duty, and session time.
- Keep coils cool; avoid continuous high power.
- Mind ears & neighbors; protect hearing.
- No HV or mains tinkering; use proper PSUs.
Clean Power Chain
- Signal gen → audio amp → load (coil/driver)
- Short leads; strain relief; avoid shorts
- Measure at source; note amp gain
- Log Vpp, RMS, freq, duty, duration
Measurement Basics
MetrologyCore Reads
- Frequency (counter), Vpp & Vrms (scope/DMM)
- THD+N (if available) or FFT check for purity
- Temperature of coils/amps under load
- Impedance awareness (amp ↔ load)
Best Practices
- Use x10 scope probes; minimize loading
- Calibrate levels with a simple reference
- Photograph setups; version your notes
- Change one variable at a time
Routing & Mixing Setups
Patch IdeasSingle-Chain (Baseline)
AWG → Amp → Coil/Exciter. Sine only. Sweep to find gentle resonances. Record Vpp and observed effects.
Dual-Channel ‘Paradox’ Mix
Ch A: base tone; Ch B: inharmonic or prime-ratio offset. Sum via passive resistors before amp, or use two amps into two spatially separated emitters.
Quadrature Drive (90°)
Ch A/B same freq, 90° phase. Useful for rotating field studies with paired coils/emitters. Keep power low.
Duty-Sweep Pulse Study
Fix freq, vary duty (10–90%) to watch spectral spread vs. pattern clarity (cymatics, coil response).
Bench Experiments
Lab NotesSine Purity & THD Check
- Set a midrange sine (e.g., 440 Hz).
- Measure Vpp/Vrms; capture FFT to check harmonic floor.
- Repeat through the audio amp into a dummy load; compare purity.
Notes: Lower THD typically yields cleaner, more repeatable coupling.
Paradox Mixing (Prime Ratios)
- Ch A: base tone (e.g., 180.3 Hz).
- Ch B: pick an inharmonic prime-ratio (e.g., ×√2 or ×φ).
- Sum with 10kΩ resistors into amp; observe beat/intermod textures on plate/coil.
Notes: Keep overall level the same as single-sine baseline for fair comparison.
Duty Cycle vs. Pattern Clarity
- Choose one modal freq on your plate/coil.
- Sweep duty 10→90% at constant Vpp.
- Log the narrowest duty that still yields a stable pattern.
Notes: Expect a tradeoff: more harmonics can excite patterns but also add noise.
Glossary (Quick)
ReferenceVpp / Vrms
Peak-to-peak voltage / effective heating equivalent.
Duty Cycle
% of period signal is high (pulses/PWM).
THD / THD+N
Total harmonic distortion; purity metric.
Impedance (Ω)
AC resistance; affects power transfer and load.
Intermodulation (IMD)
New frequencies from nonlinear mixing.
Aliasing
False frequencies from under-sampling; use filtering.
FAQ
ClarityDo I route the generator through the Fosi amp?
Yes—generator → Fosi → load. Start with low gain. Measure at the generator output and note the amp setting for consistency.
Sine or square for cymatics/coils?
Use sine for clean single-mode tests; try square/pulse when you intentionally want harmonic richness—then return to sine to lock.
Can I bridge two amp outputs into one coil?
Avoid tying two powered outputs directly together. If you need mixing, use passive summing resistors before a single amp input, or use two separate emitters.
What’s a safe starting Vpp?
Start modest (e.g., 0.5–2 Vpp at the generator), then raise gradually while monitoring heat and sound levels.
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